World leaders gather in Paris for unity rally

A massive rally is being held in Paris on Sunday as a show of unity after 17 people were killed in three days of terror in France.

Around 40 leaders from around the world, including British prime minister David Cameron and German chancellor Angela Merkel, will attend the march in the French capital.

Unprecedented security arrangements are being made for the rally, including the positioning of snipers on rooftops. France will continue to remain in a state of high alert for the next few weeks, authorities said.